New phorid fly released in fight against fire ants

Paul Schattenberg | Jul 14, 2006

There's a new phorid fly in town, and this one could be even deadlier to fire ants than other species, said a Texas Cooperative Extension entomologist.

"We've been releasing a different type of phorid fly in New Braunfels to see how effective it will be in the controlling fire ants," said Molly Keck, Extension entomologist for Bexar County. "We're hoping this one will be even more deadly to them than the other species of phorid fly we've been using throughout the state for fire ant management."

If the release is successful, additional releases of the new phorid fly species will likely be forthcoming, she said.

Phorid flies kill fire ants by "dive-bombing" them in order to lay their eggs in the ant's thorax, Keck explained. Once hatched, the fly larvae migrates into the head of the ant, eating the contents. Eventually, the ant's head falls off.

The new fly, Pseudacton curvatis, is imported from South America and has been acquired though the U.S. Department of Agriculture's Animal and Plant Inspection Service, Keck said.

An initial release of about 75,000 of these flies was completed over three days - June 14, 20 and 23 - in the southeastern part of the city.

"This type of phorid fly is different from the Pseudacton tricuspis, which is already being used in several counties as a biological fire ant control," Keck said. "It's more robust and prefers the smaller-sized worker ants. It also handles cold weather better than tricuspus, so it's less likely to die out during fall or winter."

"Those colonies usually have large numbers of the smaller worker ants in and around them," she said. "So they provide more 'targets' for this fly. And these types of colonies are abundant throughout the state."

A similar release of the new species has already taken place near Denton, but this is the first in the South Central Texas, Keck added.

"We're also trying to keep the release of the new fly far enough away from where we have released or plan to release the Pseudacton tricuspus," she said. "That way the two species won't be competing with one another. And although it's likely the two can survive in the same area, the curvatis would likely to out-compete the tricuspus in a given area, so it just makes more sense to release them far enough apart."

After the initial release, Keck will revisit the release area about every six months to check the progress of the new species in controlling fire ants. However, it may be two years before any significant evidence of the fly's effectiveness in killing fire ants and adapting to the area is visible, she said.

"We may see tangible evidence as little as a year, but sometimes it takes longer," she said.

Even if the fly proves highly effecting in controlling fire ants, it should not be viewed as a "golden bullet" for killing them, she warned.

"The new species should be seen as another weapon in fight against fire ants in the state," she said. "But we hope it will be a strong addition to the existing arsenal of chemical and biological controls in the management of fire ants, which include its predecessor: Pseudacton tricuspus."